1. Field of the Invention
The present invention relates, in general, to a method and apparatus for manufacturing pre-recorded video cassettes which cannot be copied by ordinary means without technical impairments caused by playback speed variations introduced onto the copy.
2. Description of the Related Art
The most used videotape format for program distribution to consumers is the VHS.RTM. system. Prior methods and apparatuses have been developed to produce videotapes which reproduce acceptable picture and sound when played but which produce unacceptable copies. It is believed that the current state-of-the-art for inducing technical impairments when copies of copyrighted tapes are attempted is the methods described in Ryan, U.S. Pat. Nos. 4,819,098, issued Apr. 4, 1989, and Ryan, 4,631,603, issued Dec. 23, 1986. Both of these patents disclose methods designed to "fool" the automatic gain circuits (AGCs) of video cassette recorders (VCRs).
The Ryan '603 patent discloses a method and apparatus for "confusing" or causing misoperation of the AGCs in a videocassette recorder by adding a train of pseudo-sync pulses to a video signal during the vertical blanking interval thereof, and following each pseudo-sync pulse by a positive pulse of suitable amplitude and duration, to cause the AGCs system in a given videotape recorder to make an erroneous measurement of the video signal level, and thereby cause an unacceptable recording of the video signal.
The Ryan '098 patent discloses a method and apparatus for "confusing" or causing misoperation of the AGCs in a video cassette recorder by adding a plurality of positive pulses to the video signal with each immediately following a respective trailing edge of a normally occurring sync pulse. These added pulses are clustered at the vertical blanking interval of each field to minimize the affect of the same on the viewability of the picture defined by the signal while still causing the automatic level control circuit in a recorder to assess the video level at many times its actual value.
The desired results of both the Ryan '603 patent and the Ryan '098 patent depend upon the VCR used to make the copy having AGCs, and the effectiveness of both the Ryan '603 patent and the Ryan '098 patent depends upon the responsiveness of the AGCs.
No known prior art method or apparatus discloses or suggests the present invention. More specifically, no known prior art method or apparatus for manufacturing a videotape from a video signal loops the video portion of a video signal from a video source through a sync generator means to a frame store means for providing the video portion of the video signal with new vertical positioning and blanking; passes the output video signal from the frame store means to a dual vertical sync inserter means for inserting a second vertical sync onto the video signal; and then passes the output video signal from the dual vertical sync inserter means to a modified video recorder for recording onto a videotape.
No know prior art method or apparatus discloses or suggests the present invention. More specifically, no known prior art method or apparatus discloses manufacturing a videotape from a video signal by looping the video portion of a video signal from a video source through a sync generator means to a frame store means for providing said video portion of said video signal with new vertical positioning and blanking; passing the output video signal from said frame store means to a dual vertical sync inserter means for inserting a second vertical sync onto said video signal; and then passing the output video signal from said dual vertical sync inserter means to a modified video recorder for recording onto a videotape.